Keyframes Panel
From Synfig Studio :: Documentation
The Keyframes dialog is where you make new keyframes for the animation.
These will show up in the Timeline dialog. To jump to a specific keyframe, double click on the (JMP) column. The add keyframe button adds a new keyframe to the current frame - a frame where there is no keyframe set already - and the delete keyframe removes a keyframe. The duplicate keyframe (accessed with the down arrow in the keyframes dialog) copies the keyframe to the current frame.